Patent GB-222079-A (GB)
Title: Improvements in automatic or semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1924-04-30
Abstract: 222,079. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Nelson, M. L.). Sept. 17, 1923, [Convention date]. Automatic and semi-automatic exchange systems using register-controllers of the code-translating type have the following features :-(1) The driving impulses for the sending switch are obtained from an individual pendulum interrupter started up as each digit is to be sent, and the impulses over the outgoing trunk are sent by the driving magnet. The starting circuit for sending the first numerical digit is closed only when the off-normal contacts of the second digit register change over and a corresponding arrangement is made with the third digit so that the sending switch cannot get ahead of the registers. (2) A single skip conductor on the I.D.F. enables any of the four positions in which the exchange code is sent to be skipped. (3) If dialling is unduly delayed the director is released and the calling party switched through to the first selector which, however, he cannot operate if he dials subsequently. (4) The switch that selects an idle register-controller is given a step when the register-controller is released so that in general a different one is used for the next call. (5) When the office register is set to operate selectors over a very long trunk, a resistance in the normal impulsing circuit is short-circuited. (6) In the case of toll and express calls, operators are reached in response to a particular set of dialled office digits, over different sets of trunks, according to the service to which the calling party is entitled. Express calls are made over the same trunks as local calls, the calling line being fed at the repeater over a special low resistance relay instead of the line relay as in ordinary calls. Selection of an idle register-controller and registration of wanted number. When the line switch C, Fig. 1, seizes repeater R, line relay 44 and release relay 46 energize and circuits are completed for stepping magnet 82 and switching relay 81 of the switch SS which thereupon hunts for an idle register-controller. The operation of relay 81 when an ungrounded terminal 96 is found, energizes release relay 308, Fig. 4, and dialling tone is sent back from 505, Fig. 6, over 337, 303, 74. The subscriber now dials two exchange digits followed by four numerical digits, which are repeated by relay 44. Relay 46 is made sluggish by being short-circuited when relay 44 falls back. The impulse circuit over 303 and series relay 307 is connected over wiper 333 in succession to the vertical and rotary magnets 504, 503 of the office register OR, Fig. 6, and the stepping magnets of the digit registers DR-1 - - DR-4. Fig. 4. The energization of the series relay 307 energizes the stepping magnet 331, but the wipers 333, 334 do not take a step until the magnet de-energizes at the end of each digit. After the last digit the wipers move to a dead position. Transmission of exchange code. As soon as the exchange digits have been registered, wiper 334 grounds the wire 357 to energize start relay 411 and mark the appropriate bus-bar over wiper 511 of the register OR. Relay 411 energizes the stepping magnet 651 of the sequence switch S<1> which however does not take a step until released, and releases the pendulum magnet 412 (previously energized over the release wire 302). The pendulum vibrator V now sends stepping impulses to magnet 403 of the sending switch SEN which takes a step on each de-energization and at each energization opens the bridge 404 across the outgoing trunk. The arrival of wiper 402 at the terminal marked over wiper 511 energizes stop relay 410 which bridges the trunk, puts relay 411 under control of off-normal wiper 401, releases magnet 651 to advance switch S<1>, re-energizes pendulum magnet 412 and completes a self-interrupting circuit over off-normal wiper 401 for the stepping magnet 403. The restoration of the sending switch results in the sluggish release of relays 411, 410 in succession. On the relapse of relay 410, relay 411 re-energizes and starts a second train of impulses. Four digits in all may be sent in this way, but any or all of a set of terminals on which the wipers 511 - - 514 come to rest may be jumpered to the skip conductor 510 in which case the stepping magnet 651 of switch S<1> is energized over a self-interrupting contact and the switch is driven through the positions to be skipped. The provision for skipping all the exchange code positions may be used where the first selector gives access over (say) nine of its levels to local selectors. Transmission of remaining digits and release of register-controller. In the fifth and sixth positions of the switch S<1> the circuit of the start relav 411 goes over the off-normal contacts 371 of the register DR-2. In a similar way the transmission of the third digit cannot begin until the fourth digit register is off-normal. The transmission proceeds when relay 411 energizes in the same way as for the exchange code. After the last digit, switch S<1> moves to its ninth position in which wiper 656 energizes the switching relay 309, Fig. 4, whereupon switching relay 48, Fig. 1, energizes in series with relay 47 over 303, 360, 638. Resistance 638 prevents the energization of relay 47. Relay 48 energizes magnet 82 and releases relay 81 so that when, after an interval, relay 81 falls back the switch SS takes a step and releases relays 308, 309. Relay 308 closes a self-interrupting circuit over 355, 356 for restoring the sending switch SEN and another over 352 for the sequence switch S<1>, and energizes the release magnets of the switch S, the digit registers and the office register. Transmission over long trunks. The lowest terminal in certain groups, e.g. (80), in the office register is jumpered to one of a special set of terminals so that when switch S' moves to its fourth position a two-step relay 619 operates its contacts 1, and connects the special terminal to the corresponding bus-bar so that the fourth digit is sent in the ordinary way. When the switch S' moves on again, the relay 619 operates fully over the release wire 302 as its second winding is no longer short-circuited, and short-circuits the resistance 637 which is included in the normal impulse circuit. Release of register-controller if dialling is unduly delayed. When the register-controller is seized, relay 308, Fig. 4, connects two-step relay 306 to the wire 321 and when next the cam 310 grounds this circuit, relay 306 operates its contact 312. Later, when the ground is removed, relay 306 energizes fully as its lower winding is no longer short-circuited. If the office register has not been operated when the wire 321 is grounded a second time, switching relay 309 operates over an off-normal contact of the register, the call is switched through to the first selector, and the register controller is released. Relay 48 opens the vertical circuit of the first selector which extends over 101, 102 so that subsequent dialling will not operate the selector. The usual supervisory apparatus will indicate the fact to an attendant if this condition is prolonged. Toll calls. In the system described, subscribers are divided into three classes, entitled to unlimited, limited and no long distance service, and an extra contact 18 on this line relay is accordingly left dead, grounded or grounded over a resistance. As a result, as soon as the register controller is seized, two-step relay 602, Fig. 7, energizes not at all, fully or partially according to the rights of the calling party. As shown, toll calls are made when the register OR is stepped to the terminals (60) and the digits transmitted are 292, 293 or 290 according to the condition of relay 602, which connects the third terminal to bus-bar 2 or 3 or leaves it unconnected to cause ten impulses to be sent. The fourth terminal is jumpered to the wire 603 to cause switching to occur over wiper 656 in the fourth instead of the ninth position of switch S'. Express calls, i.e. calls to an operator giving rapid service between two cities &c. located close together. In response to the digits 5, 0, the register-controller is arranged to send either 817, 818, or 819, according to the class of subscriber, to select an express operator over a particular group of trunks. This is looked after by relay 602 in the same way as in the case of toll calls but in this case when switch S' moves to its third position relay 601 energizes and short-circuits resistance 638 so that on the operation of switching relay 309, relay 47, Fig. 1. energizes and locks itself in series with relay 48 and energizes relay 42. Completion of express calls by manual operators. The extension of the call over a trunk of one of the three groups results in the lighting of a line lamp L by relay 206, the lamp being extinguished when the listening key K is thrown and relay 207 locks up energized. The operator then connects herself to the order wire OW by means of the key P and afterwards plugs into the trunk assigned, whereupon high-resistance supervisory relay 236 energizes in series with relay 205 which however does not pull up. Sleeve relay 238, when the cord CC<1> is plugged into the wanted line, extinguishes the lamp L<1> and send out ring- ing current. On reply, ringing cut-off relay 237 locks up in series with relay 238, and energizes relay 235 which short-circuits the high resistance winding of relay 236 to allow relay 205 of cordcircuit CC to pull up and reverse the current in the incoming trunk. As a result, electropolarized relay 45, Fig. 1, energizes reversing relay 41 which cuts the left-hand winding of impedance 50 into the bridge and (relays 47, 42 being operated on this kind of call as previously described) substitutes the low-wound feed relay 43 for line relav 44. Relay 43 on energizing removes the shortcircuit made on the relapse of relay 44 from relay 46. Release.